The present invention relates to smart cards and, more particularly, to a smart card which transmits its stored data by means of modulated light and comprising, memory means for holding the data as digital information; power supply means operably connected for supplying power to the components of the smart card; and, light modulation means for modulating a light beam with the data in the memory and emitting the modulated light beam for subsequent detection and demodulation.
Technology related to cards containing information which is retrievable has taken a quantum leap in recent years. In the not-too-distant past, the common "credit card" 10 of FIG. 1 has had a magnetic strip 12 applied to the back surface onto which information can be stored magnetically in the manner of magnetic recording tape, and the like as depicted in FIG. 2. The information on the magnetic strip 12 is easily read by manually moving the card 10 through a slot 14 in a reader 16 as indicated by the arrow 18 in FIGS. 3 and 4. A read head (not shown) contained within the reader 16 develops an electronic signal as the magnetic strip 12 is moved past it. More complex readers are, of course, available such a those contained in the automated teller machines (ATMs) placed for convenience at banks and elsewhere. While an ATM mechanically inputs and processes the credit card 10, the principle is still the same, i.e. the magnetic strip 12 is moved past a read head contained within the ATM.
More recently, much emphasis has been placed on so-called "smart cards". While the magnetic strip 12 of the credit card 10 of FIGS. 1 and 2 is only able to contain a small quantity of magnetically encoded information, the smart card is capable of storing and providing literally thousands (and in some cases, millions) of bits of information. Because of their ability to store and supply such large quantities of information, smart cards are becoming associated with much broader fields of use than as a simple interface medium for credit and banking transactions. For example, in Japan (where much of the smart card technology has been developed) automobile manufacturers are associating a smart card with each automobile in the process of assembly. As the car moves along the automated assembly line, the smart card provides information to the various robotic units performing the actual assembly work. A typical smart card employed in such automated processes is shown in FIG. 5 wherein it is generally indicated as 20. The data is contained in a memory 22 which can be of the random access memory (RAM) variety or the electronically programmable read only memory (EPROM) variety. RAM, of course, is easily written but subject to magnetic erasure in the same manner as the magnetic strip 12 of FIG. 2 or other magnetic recording mediums such as audio cassettes, and the like. EPROM, on the other hand, is more difficult to write initially (or modify subsequently) and such writing must be done with special equipment provided for the purpose; however, it is thereafter not easily unintentionally erasable, as by accidental exposure to a magnetic field.
The smart card 20 contains digital logic 24 connected to the memory 22, a power supply 26, and a radio frequency (RF) transmitter 28. The transmitter 28 is connected to an antenna 30 and the power supply 26 is connected to a coil 32. As the automobile carrying card 20 moves along the assembly line, it is activated by RF energy 34 at a frequency f.sub.1 which induces a voltage into the coil 32, which is then used by the power supply 26 to drive the remaining components. The logic 24 accesses the data from the memory 22 and transmits it as RF energy 36 at a different frequency f.sub.2 from the antenna 30, from whence it is picked up by the adjacent robotics gear and used in the assembly process.
As can be appreciated, the above-described RF-activated, passive, smart card 20 is expensive to produce, as is the transmitter/receiver associated therewith. Since its use is on a limited basis and in a highly profit-oriented environment wherein the relative costs are insignificant, however, these problems cause little concern. Moreover, the fact that the transmitter/receiver has to be within a few feet of the card 20 to activate it and receive the transmission therefrom, is also of little consequence because of the controlled environment wherein it is used. As can also be appreciated, however, outside of its exclusive environment, the smart card 20 of FIG. 5 is of limited practical application.
An even more recent development in the general area of smart cards is the so-called "unified" card of FIG. 6. Like smart cards, unified cards, such as that indicated as 38 in FIG. 6, contain a computer chip (i.e., digital logic 24 and memory 22); but, additionally, unified cards add a battery 40 for power, a two-line display screen 42, and a keyboard 44, so users can enter and read information without a computer terminal. Their primary use is in financial transactions and records; however, they are finding much use in portable data collection applications. In essence, the unified card 38 is a micro-miniature computer into which data can be entered at a remote location for subsequent input into a larger computer through an electrical contact 46 connected to the logic 24. There are reports that at least one manufacturer is attempting to (or actually has) put a transmitter 28 and antenna 30 onto a unified card 38', as shown in FIG. 7, such that as the information is input to the card 38' at the remote location it is simultaneously input to the computer via an RF link.
Finally, as depicted in FIG. 8, there is a class of so-called "holographic" smart cards 48 wherein the information is written into the plastic of the card 48 in area 50 in the manner that the data is written into a so-called "compact disc". The information within the data area 50 is read by passing a light beam therethrough in a scanning fashion to detect the light-passing and light-blocking pixels within the area 50. While the holographic smart card 48 of FIG. 8 much simpler than the smart card 20 of FIG. 5 and unified cards 38, 38' of FIGS. 6 and 7 and can store millions of bits of information, it suffers from two major drawbacks. One, unlike the RAM and EPROM magnetic memories, the data within the area 50, once written, is unchangeable. Additionally, the reading apparatus is complicated, expensive, and prone to errors in attempting to read the data within the area 50.
Thus, as can be appreciated from the foregoing description of the prior art, the present state of smart card technology is such that both the cards and readers are complex, expensive, and unable to be read from any distance greater than a few feet away.
Wherefore, it is the object of the present invention to provide a family of smart cards employing modulated light for the transmission of data which are simple, inexpensive, and readable from extended distances.
Other objects and benefits of the present invention will become apparent from the description contained hereinafter taken in conjunction with the drawing figures which accompany it.